When making the upgrade, I had the same error and I am guessing the error took place on the health pickups since they were not setup the same as the weapon pickups. If they were setup with a spawner I would hypothesis that the error would not take place.
But I am getting an error regarding a Cloud Project ID, I have not uploaded anything to the cloud at all so I am not sure if this is just something with the version of Unity I upgraded to or if I missed something. I am saving my work on my D drive on my computer instead of the C drive if that makes any difference.